Persons dually-diagnosed with substance abuse and mental illness have needs for long-term support that have been difficult to meet through the substance abuse and mental health treatment systems, or through traditional, single-purpose mutual aid groups. Double Trouble in Recovery (DTR) is a new and growing 12-step-help model that is designed to meet the special needs of dually diagnosed persons during their long-term recovery process. Preliminary data indicate that the DTR movement is succeeding in forming peer support groups, in engaging the dually diagnosed in such groups, and in training peer leaders to disseminate the model. The aims are: 1) To examine the process by which dually diagnosed persons initiate contact and become progressively involved in DTR and in their recoveries. 2) To develop an understanding of DTR group formation, development and dynamics. 3) To measure and document the therapeutic mechanisms through which dual recovery groups (and mutual aid groups generally) are hypothesized to improve outcomes for their participants; i.e., emotional support, teaching and active learning. 4) To conduct an effectiveness study of DTR using longitudinal research. 5) To test a theory-driven model of the recovery process among dually diagnosed persons. Substance use, mental health status, treatment compliance, and life functioning variables will be tracked longitudinally for two years in a random sample of 300 DTR members (100 new members and 200 current members with different lengths of participation). In addition, life histories will be obtained from 50 members, 25 group factilitors will be interviewed, group process in 25 DTR groups will be observed, and the development of 5 new groups will be studied over time. DTR complements formal treatment by mobilizing peer support for recovery, and serves as long-term aftercare/continuing care following intensive short-term substance abuse or mental health treatment, including encouraging psychiatric medication compliance, which helps prevent rehospitalization. For these reasons dual recovery models are receiving considerable attention from behavioral managed care providers.